1. Field of the Invention
The present invention relates to a method for transmitting data in a telecommunication system including at least one transmitter provided with a plurality of transmitting antennas and at least one receiver provided with at least one receiving antenna, which method includes a bit encoding step for generating encoded data bits, a bit interleaving step for permutating said encoded data bits, and a modulation step for producing symbols representative of the permutated bits, each symbol being represented by a predetermined number of bits intended to be transmitted over communication channels established between the transmitting and receiving antennas.
2. Related Art
Telecommunication systems in which a plurality of antennas are used at a receiver end and/or at a transmitter end of a wireless link are called Multiple Input Multiple Output systems (further referred to as MIMO systems). MIMO systems have been shown to offer large transmission capacities compared to those offered by single antenna systems. In particular, MIMO capacity increases linearly with the number of transmitting or receiving antennas, whichever the smallest, for a given Signal-to-Noise Ratio and under favourable uncorrelated channel conditions. MIMO techniques are thus likely to be used in future wireless systems intended to provide large spectral efficiencies or, alternatively, reduce the transmitting power required for obtaining a spectral efficiency equivalent to that which is obtained in current telecommunication systems. Such MIMO techniques will very likely be combined with multi-carrier modulation techniques like OFDM (standing for Orthogonal Frequency Division Multiplex) and MC-CDMA (standing for Multi-Carrier-Code Division Multiple Access) techniques, whose use in future wireless systems is also considered.
A particular type of MIMO systems makes use of a Bit Interleaved Coded Modulation technique, further referred to as BICM, according to which the transmitter includes a channel encoder intended to apply an encoding, e.g. by means of a convolutional code or of a turbo code, to uncoded data bits, and to provide an encoded bit stream to an interleaver. This interleaver will then deliver permutated bits, which are to be divided into word sequences intended to be transformed into a series of coded symbols represented each by a plurality of bits, the bits representing a same symbol being intended to be transmitted during a same time interval, called symbol period, by respective transmitting antennas.
Transmitted symbols are to be decoded on the receiver end, which is usually performed in MIMO systems of the BICM type by means of an iterative space-time decoder, which decoder is intended to produce estimates of coded bits constituting the transmitted symbols. The spatial diversity induced by the use of multiple transmitting and receiving antennas eases such a decoding, since this diversity provides a larger amount of information than that which would be provided by a single signal transmitted through a single communication channel.